The long-awaited 12-country Trans-Pacific Partnership is shaping up to be a dominant theme on the campaign trail this week, with speculation rampant that a deal is finally taking shape.

An agreement in principle could be announced as early as Friday, but it's not the first time an anticipated announcement has failed to materialize: the last round of negotiations in July ended in disappointment.

Not everyone expects the deal to be good news.

On Parliament Hill, dairy farmers walked their cows, parked tractors on city streets and dumped milk on the pavement to protest an agreement they fear will mark an end to their way of life.

Major dairy producers like New Zealand are pushing for fewer trade barriers in foreign markets, including Canada's.

Canada's supply management system -- a structure of production limits and import tariffs -- has long been a cornerstone of the profitable, economically viable family farm, Harper said during a campaign event in Kleinburg, Ont.

"This government remains absolutely committed to making sure we preserve our system of supply management through trade negotiations," he said.

"Decisions to be made on whether we have such a system or not are decisions we want Canadians to take, not foreigners to take."

Harper didn't have control over the schedule of the TPP talks, but the timing is being embraced by the Conservatives.

Their energy is focused on being able to herald a deal on the TPP by the end of the week, thereby bolstering the party's credentials on matters of international trade.

Sources say a series of events are being planned for the end of the week, but ministers were already sending out news releases Tuesday touting the advantages of a deal and quoting from supporters in the business community.

Harper also said that Canada's auto sector would be protected, but that it was important for the wider economy to be part of the negotiations. …